Adaptive Supervisory Control of Automated Manufacturing Systems With Unreliable Resources Based on Smart Switch Controllers
Ziliang Zhang, Gaiyun Liu, Zhiwu Li
Abstract
This paper proposes an adaptive supervisory control policy for an automated manufacturing system (AMS) with multiple types of unreliable resources. The considered AMS is a generalized system of simple sequential process with resources (GS <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{3}$</tex-math> </inline-formula> PR). In order to model resource failures and recoveries, modified recovery subnets are developed, which model more complex resource failure scenarios compared with traditional recovery subnets. For the purpose of guaranteeing the execution of a system’s production successfully, from the perspective of the structural analysis of the system, a siphon control-based technique is introduced and a type of controller is developed. It is verified that the proposed adaptive control policy assures the deadlock-freeness of the controlled system no matter if there exist resource failures, and retains all behavior of the original system. Finally, examples are presented to demonstrate the proposed method. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —Resources failures are ubiquitous in an automated manufacturing system (AMS). Their occurrences can lead partial or global system stagnation, which causes unnecessary downtime and even catastrophic results. Most of the existing robust deadlock control strategies for AMSs with unreliable resources usually restrict system evolution in an unnecessarily conservative way such that part of permissive behavior is excluded if no resource failure occurs, which affects the utilization of resources and reduces the productivity of the system. In order to address the issue, this work considers a type of AMSs where each processing stage may require an arbitrary number of units, but all from a single resource type. For such an AMS, we propose an adaptive deadlock control policy that makes the controlled system deadlock-free, keeping all the system behavior as in the case that unreliable resources do not break down. The proposed method is realized by dynamically adjusting the working modes of a system to adapt to resource failures and recoveries, which is readily accessible to practitioners from a technical viewpoint.